Mothers can spread yawns to their yet-to-be-born offspring during pregnancy, researchers report May 5 inย Current Biologyย the first empirical evidence that behavioral contagion, long thought to be a social phenomenon of postnatal life, may have roots in the womb.
Yawning is contagious among many social creatures, including humans, dogs, lions and parakeets. While the behavior is generally thought to boost blood flow to the brain for cooling and alertness โ the so-called thermoregulatory hypothesis โ yawning could also help synchronize group movements and serve as a primitive form of empathy. Brain-imaging studies have linked contagious yawning to several regions associated with social cognition and emotional mirroring, including the ventromedial prefrontal cortex, superior temporal sulcus, amygdala, and insula โ the same network involved in mother-infant bonding.
And yawning begins even before birth. Human fetuses have been observed yawning as early as the eleventh gestational week, making it one of the earliest coordinated behaviors to emerge in development. These prenatal yawns indicate harmonious progress in the development of both the brainstem and peripheral neuromuscular function, and appear linked to an ultradian rhythm of vigilance. They also exercise the muscles and neural circuits that will later be essential for breathing and swallowing. Yawning frequency follows a U-shaped developmental pattern โ premature infants yawn more frequently than term babies, suggesting the reflex gradually becomes refined and integrated into a broader behavioral repertoire.
But researchers had largely attributed these prenatal yawns to endogenous body programming, a kind of automatic neural housekeeping distinct from the socially contagious reflex that strikes children and adults. Notably, children are immune to contagious yawning until around five years of age, suggesting the social dimension of yawning develops gradually after birth. Whether a mother’s yawning had any impact on the fetus remained entirely unknown.
Pregnancy is a time when mothers and their fetuses are inextricably linked not just physiologically, but perhaps behaviorally, says Giulia D’Adamo, a neuroscientist and psychologist at the University of Parma in Italy. “During pregnancy, everything is groundwork for what is going to happen next.”
To test whether fetuses catch yawns from their mothers, the researchers recruited 38 pregnant women between 28 and 32 weeks along, all with healthy, uncomplicated pregnancies, and showed them three different types of video in a quiet room: a yawning video, a mouth-movement control video, and a still-face control video. A video camera monitored the mother’s face while a 2D ultrasound provided a real-time view of the fetus’s nose and lips. Three expert coders, who did not know what the mother was watching, reviewed and verified the yawns. The researchers also used DeepLabCut, an AI-based motion-tracking tool, to precisely quantify subtle lip and nose movements and train a neural network to distinguish true yawns from other mouth openings.
Roughly 64 percent of the mothers yawned during the contagion condition โ a proportion higher than the 40 to 60 percent typically reported in the general population, consistent with prior research suggesting that pregnant women are especially susceptible to yawn contagion, possibly due to hormonal and neurobiological changes that heighten sensitivity to social and emotional stimuli. Just over half of the fetuses responded to their mothers, yawning themselves around a minute and a half later โ well within the roughly five-minute window in which humans are susceptible to catching a yawn. That fetal yawn was far more likely to follow a maternal one than to happen spontaneously. True mother-fetus pairs exhibited stronger temporal coherence than recombined dyads โ pairs artificially matched across different sessions โ ruling out coincidence and pointing to a genuine dyadic signal.
The channel through which the yawn travels remains unclear. It’s possible that the physical movement of a yawn puts pressure on the uterus in ways that signal to the fetus that it should yawn too, D’Adamo says. Hormonal messengers oxytocin, which plays a central role in maternal bonding and is already elevated during pregnancy, is one candidate could also prompt a fetal yawn. Future studies examining women at various stages of pregnancy, and directly measuring hormonal changes during maternal yawning, could help uncover the mechanism.
These findings challenge the view of fetal behavior as purely reflexive or entirely self-contained, the authors write, and instead paint a picture of a fetus whose behavioral expression is already woven into a shared biological context with its mother. The study suggests that examining maternal behavior and its impact on fetal action may help clarify the earliest foundations of co-regulation and embodied development, which later support motor and social competencies after birth.
But for now, it’s unclear whether fetuses catching yawns serves any direct adaptive purpose, or if those early echoes simply reflect the deep physiological entanglement of mother and child. The real social context, D’Adamo says, happens after birth.
Reference:
Giulia D’Adamo et al, Prenatal behavioral contagion through maternal yawning and fetal resonance, Current Biology (2026). DOI: 10.1016/j.cub.2026.04.025
Journal information: Current Biology
